The present invention relates generally to air filters, and in particular, relates to air purification systems for commercial kitchens.
Air purification systems are primarily used to extract impurities, such as grease, from grease-laden air formed in commercial kitchens and other similar environments during cooking. Grease extractors are typically a cleanable or replaceable component of kitchen ventilation systems disposed above a cooking area, such as a stove or the like. A fan in the ventilation system draws grease-laden air through the filter media which extracts the grease from the air prior to exhausting the air into the atmosphere. The extracted grease may run down the filter wall and be collected for proper disposal, or the grease may be trapped within the filter media that may be subsequently cleaned.
Conventionally, a primary air filter is mounted onto the hood of a cooking area for the removal of large grease and other airborne particles before the air travels through the ductwork of a building and is ultimately expelled into the outside environment. A secondary air filter is located at the outlet of the building's ductwork to remove additional smaller air impurities before the air is released. Various filters are available for such an air purification system.
Conventional centrifugal air filters cause air to enter a helical path in a vortex chamber and subject the impurities to a centrifugal force. The impurities are propelled away from the vortex center and impinge upon chamber walls. The air exits the vortex chamber leaving the impurities behind in the chamber. One such centrifugal air filter is described in U.S. Pat. No. 6,251,153 entitled “Centrifugal Air Filter” the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein. Centrifugal air filters are advantageous in that the extracted air impurities run down the filter wall and are collected for proper disposal, thereby minimizing the need for cleaning and other maintenance efforts that could cause down-time. While air filters of this type are effective at removing large air impurities that may be flung against the side of the filter, smaller impurities may remain in the air and travel into the ductwork and fan of the building.
Baffle filters define an enclosure having an inlet that receives grease laden air. The enclosure defines a plurality of baffle plates that force the air to abruptly change the direction of travel several times prior to exiting the filter. As the air changes direction, grease and other impurities are propelled away from the air stream and impinge upon the chamber walls. The grease may then run down into a collection cup.
Another type of filter, known as an impact filter, traditionally includes a wire mesh bed packed with filtration particles. As air is drawn through the impact filter, the media will trap impurities therein such that a cleaner air is output. While impact filters are successful at removing both large particles suitable for a centrifugal fan along with smaller particles that may escape a centrifugal fan, depending on the filter media, they often accumulate a significant amount of dirt in a relatively short period of time. The accumulation presents a blockage to the air passing therethrough, which produces a significant pressure drop across the filter and limits the air flow rate through the purification system and ultimately the cleanliness of the air passing through. Impact filters thus require frequent cleaning and maintenance.
While such air purification systems are suitable for their intended purpose, grease and other volatile organic compounds (VOC's) tend to accumulate within the ductwork, thereby necessitating frequent maintenance and cleaning.
It is thus desirable to provide a reliable air purification system that removes both large and small particles from the air prior to the air entering a building's ductwork.